In a baler, straw, hay or other crop material is picked up from the ground by a pickup system and supplied to a feeder system, e.g., a rotor, which propels the straw into the baling chamber, where it is compacted and formed into bales. The pickup system and the feeder may alternatively be part of an in-feed or transport element for other crop processing means. The feeder and pickup system are connected to rotate in the forward direction at the same time as one another. Typically, a shaft of the rotor which is driven by way of first sprocket by, for example, a tractor PTO (power take-off) shaft, carries a second sprocket which is connected to drive the pickup system. The present invention is particularly concerned with the construction of the coupling mechanism that is suitable for coupling the rotor to the second sprocket driving the pickup system.
A requirement of the coupling between the feeder drive and the pickup system is that it must be disengaged automatically in the event of an obstruction in the pickup system.
A coupling is known which comprises discs rotatable with the rotor shaft and disposed adjacent the pickup system drive sprocket. The disc and the sprocket are connected to one another by a shear bolt inserted through bushings affixed to the disc and sprocket. The bolt shears when the torque transmitted through the coupling exceeds a preset maximum and thereby automatically disengages the drive to the pickup system when a serious obstruction is encountered.
A problem that is experienced with this form of coupling is that after the bolt has sheared it is necessary to realign the bushings in which it fits before it can be replaced by a new shear bolt. As the disc rotates with the feeder and the other with the pickup system, one of these two has to be rotated to achieve the required accurate alignment of the holes and having regard to the size and mass of these two items, this is a task that requires the use of large wrenches or levers. Such means are not readily available when operating the baler in the field.